docs: def p_jsonpath_named_operator(self, p):
          "jsonpath : NAMED_OPERATOR"
          if p[1] == 'this':
              p[0] = This()
          elif p[1] == 'parent':
              p[0] = Parent()
          else:
              raise Exception('Unknown named operator `%s` at %s:%s' % (p[1], p.lineno(1), p.lexpos(1)))